Robust Adaptive Tracking Control Design for the Mechanical Sandwich Systems Subject to Sandwiched Saturation Function

In this paper, the adaptive robust tracking problem is solved for the sandwich systems with non-smooth nonlinear saturation function in the presence of uncertainties and external disturbances. Sandwich systems are a class of nonlinear systems, such that the non-smooth nonlinear functions are sandwiched between their distinct subsystems. This article studies on sandwich systems include two nonlinear subsystems with the nonlinear saturation function located between the subsystems. Due to features like the lack of invertibility and non-smoothness of the saturation function, as well as the existence of unknown gains and external disturbances, analysis and design process for the mentioned systems face with complexities. In this paper, an adaptive robust controller is proposed by using the backstepping control approach and its combination with the Nussbaum function, based on the Lyapunov theory to achieve the control objectives. In order to verify the theoretical achievements as well as, the efficiency of the proposed method, it’s applied to a mechanical system consists of a one-link manipulator that is handled with a DC motor. Simulation results show the effective performance of the proposed approach in the tracking of the time-varying reference signal in the presence of unknown terms, external disturbances and sandwiched saturation function between subsystems.